The present invention relates to a top cap for power nailers and has seals fixedly engaged with flanges of the top cap and the piston is reciprocatingly moved in the top cap and does not scrape the flanges.
A conventional top cap 1 of a power nailer is shown in FIG. 1 and generally includes a piston 2 reciprocatingly received in the interior 10 of top cap 1. Two annular flanges 12 extend from an inside of the top cap 1 so that the tubular body of the piston 2 is movably engaged with the gap between the two annular flanges 12. Two grooves 20 are defined in an outer periphery and inner periphery of the body so that two seals 21 are respectively engaged with the two grooves 20. The two seals 21 are moved along the surfaces of the two annular flanges 12 when the piston 2 is moved. A communication path 13 is defined through the top cap 1 so as to push the piston 2 downward and the air escapes from the hole 11 when the piston 2 moves upward. The top cap 1 is made from Magnesium Alloy so that a metal coating is coated on the top cap 1. The frequent movement of the seals 21 on the surface of the Magnesium Alloy wears out the metal coating so that the Magnesium Alloy becomes to be fragile.
In accordance with one aspect of the present invention, there is provided a An assembly of a top cap and a piston a power nailer. The top cap comprises a communication path defined through the top cap and communicating with an interior in the top cap so that a piston is movably received in the interior. A hole is defined through a top of the top cap and communicates with the interior. Two annular flanges extend from an inside of the top cap and an annular space is defined between the two flanges. Each of the two flanges has a groove defined therein and the two respective grooves communicate with the annular space. Two seals are respectively engaged with the two respective grooves. A tubular body of the the piston is engaged with the annular space and contacts the two seals. A spring is biased between the piston and an inside of the top cap.
The primary object of the present invention is to provide a top cap that has fixed seals in the flanges and the piston movably contacts the seals so that the flanges will not be worn out.